There are two ways the U.S. can arm an ally such as the Kurds. It can donate, or sell cheap, the latest U.S.-made weaponry. Or it can send foreign-made weaponry — Russian usually — through a middleman.
The U.S. military recently grounded all of its new F-35 Joint Strike Fighters after one caught fire on a runway. There is reason to worry that basic design flaws vex what is on track to become the military's most numerous warplane.